How a Daubert Motion Works

Where the motion sits on the calendar

A motion to exclude is not an event that happens to a case. It is the last stage of a sequence that starts with a disclosure deadline, and each earlier stage narrows what the motion can say.

Absent a stipulation or a court order, Rule 26(a)(2)(D) sets expert disclosure at least 90 days before the date set for trial, with rebuttal disclosures due within 30 days after the disclosure they answer. In practice almost every case runs on a scheduling order that supplies its own dates and often splits them by side and by issue. The report is served on that date, and under Rule 26(b)(4)(A) the deposition of a witness required to provide a report may be taken only after the report is provided.

Then the deposition, which decides most motions. The report tells you what the expert concluded; the deposition tells you whether there is a method underneath it. An expert who cannot state which export a number came from, what the comparison period was, or what else was examined in the window has produced the motion's best exhibit himself. By the time briefing opens the record is closed, consisting of the report, the materials produced as facts or data considered under Rule 26(a)(2)(B)(ii), and the transcript.

The filing date comes from the court's order — commonly the deadline for motions in limine, and commonly at or near the dispositive motion deadline. Read the order carefully: some judges set a separate, earlier deadline for Rule 702 motions so that the summary judgment record is settled before it is briefed.

Why it is often argued next to summary judgment

The two motions are separate in form and frequently inseparable in effect. Where a party's causation case rests entirely on the expert — and in a traffic loss matter it very often does, because nobody else can say why organic visibility moved — a ruling striking the causal opinion leaves nothing for the jury to weigh on that element.

That connection drives real scheduling decisions. A party moving to exclude usually wants the Rule 702 ruling first or simultaneously, so the summary judgment record is evaluated without the challenged opinion; a party defending the expert usually prefers the opposite sequence, or a record in which the opinion is one of several routes to the same fact. Whether either is available depends on the judge's practice, which is worth learning before the schedule is negotiated rather than after.

A motion in limine and a full Rule 702 motion are not the same instrument

Both can end with an expert not saying a thing to a jury, and they work differently.

A motion in limine is a pretrial evidentiary motion, usually short, usually one of a numbered set, and usually aimed at a defined piece of testimony or a specific exhibit: a chart built from an undisclosed export, a reference to an industry guide published after the conduct, a dollar figure the witness is not qualified to compute. Rulings are frequently provisional, expressly subject to revisiting at trial in context, and they do not necessarily require findings about the witness's methodology at all.

A full Rule 702 motion attacks the opinion at its foundation and asks the court to make Rule 104(a) findings — that the proponent has not shown, more likely than not, that the testimony rests on sufficient facts or data, is the product of reliable principles and methods, or reflects a reliable application of them. It is longer, usually supported by excerpts of the transcript and often by a rebuttal expert's declaration, and it produces a written ruling that shapes the trial.

The choice is strategic rather than doctrinal. Where the technical work is sound and only the damages sentence overreaches, an in limine motion aimed at that sentence is proportionate and more likely to be granted than an attempt to strike the whole witness. Where the analysis has no stated method at all, a narrow motion wastes the strongest argument available. Filing both is common.

Who has to prove what

Since 1 December 2023 the text of Rule 702 states that the proponent must demonstrate to the court that it is more likely than not that each of the four conditions is satisfied. That was already the Rule 104(a) allocation; putting it in the rule changed how the briefs read.

Two practical effects. The movant's job is easier than it used to be, because identifying an unfilled gap can be enough — the movant does not have to prove the opinion wrong, only that the showing has not been made. And the familiar response that a weak basis or a shaky application goes to weight and belongs on cross-examination is much harder to sustain, because the Advisory Committee said in terms that treating the sufficiency of an expert's basis and the application of the methodology as questions of weight is an incorrect application of Rules 702 and 104(a).

None of that converts every criticism into a ground for exclusion. Disagreement about which comparison period to use, or whether a confound explains as much as the opposing expert says, remains cross-examination material. The line, imperfect but workable, is between an opinion the method can support and one it cannot: a defensible choice among reasonable options goes to weight, and a missing step goes to admissibility. Rule text is at Cornell LII.

Whether there is a hearing

There is no entitlement to an evidentiary hearing on a Rule 702 motion. Whether to hold one is committed to the court's discretion, and many are decided on the papers.

Courts are likelier to hold a hearing where the reliability question turns on something the transcript does not settle — an unfamiliar technique, a genuine factual dispute about what the expert did, or competing experts describing the same data incompatibly. They are likelier to decide on the papers where the defect is visible in the report itself: no stated sources, no stated date ranges, a conclusion with nothing between it and the underlying work.

Do not plan on a hearing as the place to cure a problem. The report has already fixed what the opinion is, and testimony supplying a method the report never described raises its own disclosure objection. The deposition has already recorded what the witness said when unprepared. And a hearing gives the movant a second sworn examination on the exact points it has spent months developing.

Where one is held, expect it to track the elements: what the witness looked at, over what period and against what comparison, what was excluded and under what rule, what else could explain the result and what was done to test it, whether the analysis can be reproduced, and where the opinion stops. Some courts will also permit voir dire of the expert at trial, before the opinion is given — a narrower proceeding with the jury out and a much shorter runway.

Partial exclusion is the realistic outcome

Parties brief these motions as though the result is binary. It usually is not. In this field the characteristic ruling cuts the causal or quantified opinion and leaves the descriptive one standing.

What that looks like in an order: the witness may testify that on a stated date a stated set of URLs ceased to be returned in the index, that the redirects from the retired addresses resolved to a 404 rather than a 301, and that a noindex directive remained in the deployed templates for a stated period. The witness may not testify that those defects caused the plaintiff's revenue decline, or to a percentage of the decline attributable to them, because the report did not test the core update that landed in the same window.

Three consequences follow, and they are the reason to think about the structure of a report long before the motion.

• The trial changes shape. Someone else has to carry causation — often a damages expert who can take the surviving technical findings as inputs, sometimes fact witnesses, sometimes documents. If nobody can, the partial ruling functions as a full one.
• Scope orders are policed by objection. A witness permitted to describe but not to attribute will be interrupted at the first sentence that drifts, and drifting in front of the jury after an adverse ruling is a bad look that the opposing side will be glad to create.
• Separable opinions survive better. Technical findings stated on their own data, with the economic consequences developed separately, are far more likely to withstand a defect elsewhere than a single narrative in which the last sentence depends on every previous one.

Other partial outcomes recur too: an opinion admitted with a specific exhibit excluded because its underlying export was never produced; an opinion limited to a defined date range because the data outside it was modeled rather than measured; an opinion admitted subject to the witness first laying a foundation at trial.

What follows the ruling

An exclusion order is not necessarily the end of the subject. Reconsideration is available where the ruling rests on a misunderstanding of the record, and it is a genuinely different motion from an attempt to supply a method the report never contained. A proponent whose opinion is excluded will usually want to make an offer of proof preserving the substance for appeal, and an in limine ruling described as provisional can be revisited at trial once the context has developed.

Where the opinion survives, Rule 703 governs when an expert may disclose to the jury facts or data that are themselves inadmissible, so a court admitting an opinion built partly on third-party material may still keep that material from the jury or admit it with a limiting instruction. The questions that failed to produce exclusion are frequently the best available for cross, because the court has heard them once and the witness has answered them once on the record.

There is also a settlement dimension nobody briefs. Where causation depends on one expert, the Rule 702 ruling is often the last piece of information either side is waiting for, and the case resolves shortly after it issues in either direction.

The decisions counsel actually makes

Four.

Whether to move at all. A denied motion leaves the opposing expert testifying with a reliability ruling behind him, and it tells the other side exactly which weaknesses you have found while there is still time to shore them up at trial. Where the defects are matters of degree rather than missing steps, cross-examination on scope is frequently the better instrument.

What to aim at. The whole witness, one opinion, or one exhibit. Overreach is the common error: a motion attacking everything invites an order denying everything, and it obscures the one argument that would have carried.

Whether to support it with a rebuttal expert. A rebuttal report that re-runs the opposing analysis on the produced files and reaches a different number is a materially different exhibit from a brief arguing in the abstract. It also has its own disclosure deadline, so the decision has to be made well before the motion is due.

What the record must already contain. If the argument is that a figure cannot be reproduced, the request for the underlying exports has to have been made and answered on the record. If the argument is that the witness considered material never produced, the deposition has to have established what was considered. Motions fail on this more often than on the law — the argument was right and the record did not support it. These are litigation judgments, and they are counsel's to make, usually with someone who can work the other expert's data rather than only read the prose.

Frequently Asked Questions

Published 2026-08-11